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Douglas Denny, you wrote:
"I can understand too that modern GPS engines are going to calculate faster 
and so give less delay - but nevertheless there is no excuse whatever that 
the display time can, with no effort needed by the designer, be _exact_ and 
displayed as such or flagged as U/S until correct.  It is really rather silly 
to have a piece of kit which receives signals of time to within a few 
nanoseconds, knows it,  and cannot display it accurately"

But this is just a market demand issue (and market demand drives product 
specifications, right?). The vast majority of GPS users are looking for 
position information primarily, and the time from the device is just a bonus. 
Very few GPS users require time accurate to the nearest five seconds, let 
alone the nearest tenth of a second. Who would use that information in a 
handheld GPS unit or any unit designed fundamentally for position-finding? Of 
course, there are entirely different market segments out there, like mobile 
phone companies, for whom the exact time is actually the most important 
product in the GPS signal. It all comes down to demand. I agree that it's 
ironic that the exact time is in there, hidden away somewhere, but I don't 
agree that it's "silly" we can't see it. It's like my previous cell phone 
which had a GPS receiver and knew its position accurately but had no way to 
display it (this was a marketing choice by the manufacturer and the service 
provider). But it DID have extremely exact time displayed --accurate to the 
nearest tenth of a second quite reliably. This was derived from the cell 
towers' clocks apparently, and presumably the towers got it from specialty 
GPS hardware.

On the other topic in this thread, Internet time can be very good. One of my 
favorite older web sites, the satellite tracking site at 
www.heavens-above.com, recently added a little tool that provides properly 
synchronized time accurate to "better than" one tenth of a second. I tested 
it from my PC against WWV just tonight, and it seemed to be that accurate. 
Then I tested the same web page from the web browser in my current smartphone 
(two years old so therefore "a dinosaur"). That same tool in the phone 
browser could not keep up. The initial time was about right, but the ticking 
seconds after that were in some kind of time warp and fell thirty seconds 
behind after one minute. The phone's internal time (not from the Internet) 
can be up to fifteen seconds off which is not good enough for celestial 
navigation experiments, but certainly good enough for any practical tasks I 
do in my day.

-FER




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